Fiber optic rail monitoring apparatus and method

ABSTRACT

Systems and methods for are described for the detection of breaks in railroad track rails as well as other events. A plurality of fiber optic monitoring assemblies are located proximate a section of railroad tracks. The monitoring assemblies are capable of detecting and recognizing a rail break event. In an alternative embodiment, systems and methods are described for detection of flat spots on rail car wheels.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates primarily to devices and methods used for the detection of breakages and other failures in railroad trackage. In other aspects, devices and methods are described for the detection of deformations in railroad car wheels.

[0005] 2. Description of the Related Art

[0006] Railroad tracks are made up of a pair of parallel, metal rails and a plurality of cross ties which extend between the two. If one of the metal rails breaks or ruptures, the track is unsafe since rail traffic encountering the break can be derailed. The energy released during the break of a metal rail is typically very great since the break usually occurs when the rail is snapped under very significant amounts of tension. A break in a rail during winter months, when the metal of the rails tends to shrink, can leave a separation between the two ends of the broken rail of up to several yards. As a result, it is of critical importance to be able to detect a rail break as soon as possible, so that rail traffic can be stopped or diverted and the break repaired.

[0007] Railroads use various methods to try to detect broken rail segments in their track system. The most basic and manpower-intensive method is physical inspection of the track. Because of the sheer length and number of tracks in existence today, however, this method is simply impractical.

[0008] Electrical circuitry systems are known that employ current impressed on a track segment to detect faults in the segment. An example of this type of system is described in U.S. Pat. No. 4,117,463 entitled “Circuit Fault Detection Apparatus for Railroad Track Circuit Redundant Connections.” Operation of this type of electrical monitoring system is accomplished by applying current into the wiring to form a complete circuit. The circuit is typically monitored by a wayside detector. A fault along the track segment, such as a break in the metal rail, causes an interruption of the circuit that, in turn, activates an appropriate alarm. This type of electrical monitoring system is also used for the locating of train traffic along a rail segment. However, if a break occurs over a metal tie plate, the electric circuit may be maintained and a false indication of continuous integrity is received by the monitoring equipment. A false indication of integrity will also be provided if the rail fails to break completely, although a serious compressive fracture may be present.

[0009] Ultrasonic detection devices are also known for inspecting rail welds in a track. A device of this type is detailed in U.S. Pat. No. 3,960,005 entitled “Ultrasonic Testing Device for Inspecting Thermit Rail Welds.” Unfortunately, these devices are primarily used for detecting flaws in welds and rail rather than actual breaks. Ultrasonic inspections attempt to locate rail defects which will potentially propagate into actual rail breaks in the future. As a result, real time information is not provided as to actual breaks. Additionally, rail in northern climes may have very small defects which are not detected by ultrasonic inspection but, subject to significant additional stresses cause the rail to break at unexpected locations and times.

[0010] In addition, ultrasonic inspection requires track occupancy. Train operations cannot be conducted on the section of track which is being inspected, and inspection of long segments of track can prove very time consuming. Rail sections which are used more often, or which carry a higher tonnage, require a higher frequency of inspection. Since the rail section is very busy, it can be extremely difficult to schedule such inspections without impacting rail operations for the section.

[0011] Recent developments in alternative train locating systems, such as those involving global positioning systems (GPS), may reduce or eliminate the need for electrical train locating systems, such as that described above. Unfortunately, these alternative systems do not provide a means for detecting rail breaks or other faults. Therefore, the widespread use of alternative train locating systems may be constrained by the continued need to leave the electrical system in place to monitor rail breakage.

[0012] Experimental work involving the use of fiber optics and lasers for the detection of rail breaks has been conducted recently at the University of Illinois at Urbana-Champaigne. In this experimental work, an optic fiber was directly adhered to a section of railroad rail and low coherence laser light was pulsed through the fiber. The experimentation included the testing of different types of glues for use as the bonding agent for adhering the fiber to the section of rail. Due to the direct adherence of the fiber to the rail, a break in the rail would also be expected to physically sever the optic fiber. An optical time domain reflectometery (OTDR) break detector, of the type used for detecting breaks in telecommunications optic fibers, was employed to determine when the fiber was severed.

[0013] A system of this type has many drawbacks. Perhaps most important is the fact that a breakage of the rail causes a severance of the fiber. In order for the system to become operational again, the fiber would have to be replaced or spliced and then rebonded to the repaired rail.

[0014] Further, the bonding agent can deteriorate over time allowing the fiber to become loosened from the rail and, thereafter, damaged by environmental hazards. Since optical fibers are extremely thin and somewhat fragile, the damage could occur easily. Even when bonded to the rail, the fiber is vulnerable to damage from environmental hazards such as vandalism or tampering. Also, repair work or replacement of sections of the rail will necessitate breakage and replacement of the fiber.

[0015] Thus, a need exists for a workable alternative system and method for monitoring. The present invention addresses the problems inherent in the prior art and provides a system and method for monitoring rail sections without requiring electrical circuitry.

SUMMARY OF THE INVENTION

[0016] The present invention relates broadly to the use of fiber optic technology as applied to railroad track and traffic monitoring. In an exemplary described embodiment, fiber optic based monitoring assemblies are used to detect localized disturbances occurring along a section of track. Specifically, the monitoring assemblies are capable of detecting breaks in a particular portion of a rail section.

[0017] In preferred embodiments, the monitoring assemblies are disposed in series proximate a section of rail or track. The assemblies adjoin one another so as to monitor the continuous length of the rail section. Each of the monitoring assemblies includes fiber optic intrusion sensing apparatus having extended linear sensing fibers. Each of the monitoring assemblies are capable of determining the approximate location along the rail segment wherein a break event has occurred.

[0018] Wavelet analysis is used by the monitoring assembly to identify the disturbance caused by a rail break and to distinguish that event from other potential disturbances. In the described preferred embodiments, the monitoring assemblies also include a storage media within which is recorded the fact and approximate location of a rail break.

[0019] Another aspect of the invention is described in which the fiber optic monitoring assemblies are used to detect other identifiable disturbance or conditions. For example, the assemblies could be used to detect the presence of rail cars having flat spots on their wheels.

[0020] Thus, the present invention comprises a combination of features and advantages which enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein:

[0022]FIG. 1 is a sketch depicting exemplary rail break detection apparatuses located alongside a section of track.

[0023]FIG. 2 is a schematic view showing the components of an exemplary monitoring apparatus.

[0024]FIG. 3 is a schematic view of an exemplary external cavity semiconductor laser as used in the monitoring assembly of FIG. 2.

[0025] FIGS. 4A-4D depict exemplary signals being processed and analyzed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring first to FIG. 1, an exemplary rail break detection system, indicated generally at 10, is shown positioned alongside a section 12 of railroad track. The track section 12 is composed of a pair of sections of longitudinal metal rails 14, 16 that are disposed in a parallel relation to one another. A plurality of cross-ties 18 extend between the rails 14, 16. The track section 12 is shown containing a break 20 in one of the longitudinal metal rails 14. It will be understood that the section 12 is but a small portion of a larger rail system.

[0027] A plurality of monitoring assemblies 22, 24 are disposed proximate to and substantially parallel to the track segment 12. The assemblies 22, 24 are located adjacent one another so that essentially the entire length of track segment 12 has a monitoring assembly located parallel to it. Although only two such assemblies are shown, it will be understood that as many assemblies are used as needed to adequately cover the length of the track segment 12. The monitoring assemblies 22, 24 each include a protective housing 26 and two optic sensing fibers 28, 30 that extend from the housing 26 in opposing directions.

[0028] The ends of the sensing fibers from adjoining monitoring assemblies preferably overlap one another slightly to ensure complete monitoring of the track segment 12.

[0029] The monitoring assemblies 22, 24, including their sensing fibers, are preferably buried in the ground 32 adjacent the track segment 12 approximately 2 feet below grade. The monitoring assemblies 22, 24 can be placed much closer to the track segment 12 than 2 feet and still be operable. However, close placement to the track segment 12 is not recommended currently since such close placement would probably require the sensing fibers 28, 30 of the monitoring assemblies to be buried within the ballast of the track segment which would be costly to accomplish. Further, close placement of a monitoring assembly to the track segment 12 increases the risk that the monitoring assembly might be physically damaged during a rail break event or other event. Although the length of the fibers 28, 30 is shown to be rather short in FIG. 1, it should be understood that this is merely for the purpose of depicting the invention. In practice, the fibers 28, 30 can actually extend a significant linear distance (15-30 miles) outward from the protective housings 26.

[0030] Construction and operation of the monitoring assemblies 22, 24 is understood with reference to FIG. 3 in which an exemplary monitoring assembly 50 is shown. Although the monitoring assemblies 22 and 24 are shown each having two sensing fibers 28, 30, only a single fiber is described with the exemplary monitoring assembly 50. The mechanics behind use of only a single fiber is described for clarity and simplicity. It will be understood by those of skill in the art that the use of two optical fibers could be supported by doubling the number of relevant components within the monitoring assembly.

[0031] The exemplary monitoring assembly 50 includes a fiber optic intrusion sensing system that is capable of detecting the approximate location of a disturbance or intrusion along a length of sensing fiber 52. A high level schematic diagram of a currently preferred embodiment is depicted in FIG. 2. An optical fiber 52 extends outwardly from the protective housing, which is shown schematically at 56. The housing 56 encloses a laser and detector 58 that produces light pulses of relatively high coherence which are injected into the optical fiber 52. The laser of 58, which will be described in greater detail shortly, is preferably an external cavity semiconductor laser that provides a coherent or nearly coherent laser light.

[0032] The detector of 58 provides an analog electrical signal 60 to an analog-to-digital converter 62 that converts the analog signal 60 into a digital signal 64. The analog signal 60 is indicative of received backscattered laser light from the fiber 52, and the specifics of the signal will be described in greater detail shortly.

[0033] A rotary buffer 66 stores the digital signal 64. Presently, the rotary buffer 66 preferably comprises 2 gigabytes of memory storage. Stored signals 68 are selectively provided from the buffer 66 to a signal analyzer 70. The signal analyzer 70 is preferably a signal processor similar to that described in U.S. Pat. No 5,262,958 entitled “Spline-Wavelet Signal Analyzers and Methods for Processing Signals” issued to Chui et al. As will be described in further detail shortly, the signal analyzer 70 decomposes an input signal into splines and wavelet coefficients whereupon distinctive events, such as material separation, may be identified. This “wavelet analysis” permits signal analysis to be performed in nearly real time.

[0034] The signal analyzer 70 provides a template signal 72 to a comparator 74 which compares the template signal 72 to a reference signal 76 which is maintained in a storage medium 80. The comparator 74 preferably comprises a software algorithm that determines whether the template signal 72 matches the reference signal 76 within a predetermined degree of confidence. The comparator 74 produces an output signal 82 depending upon the result of the comparison between the two signals. For example, if the template signal 72 matches the reference signal 76 within the predetermined degree of confidence, a positive signal is generated. If not, a negative signal is generated.

[0035] Generally, the laser 58 of the monitoring assembly 50 incorporates a photodetector that receives backscattered light from a pulsed laser in the system. Disturbances of a sensing fiber associated with the system will cause a change in the pattern of light received at the photodetector, thus resulting in a detected signal for the event causing the disturbance of the sensing fiber. One particularly preferred type of fiber optic intrusion sensing system is similar to that described in U.S. Pat. No. 5,511,086 entitled “Low Noise and Narrow Linewidth External Cavity Semiconductor Laser for Coherent Frequency and Time Domain Reflectometry” issued to Su and assigned to the assignee of the present invention. That patent is incorporated herein by reference. This system is characterized by a very narrow linewidth and low noise external cavity semiconductor laser useful for sensitive frequency and time domain reflectometry.

[0036] Referring now to FIG. 3, the structure and operation of an exemplary laser 58 is described in further detail. A coherent optical radiation or light beam 102 is generated by a light source 100, such as a semiconductor optical amplifier. Power supply 101 provides a pulsed current to the light source 100 so that a pulsed laser light is produced. As will be discussed in further detail shortly, it is preferred that the laser light beam be pulsed on a very short periodic time schedule. It is particularly preferred that the light beam 102 be produced at least once every millisecond (ms). The wavelength of the light beam 102 may be set according to application requirements, and may include wavelengths of 1.3 μm, 1.5 μm, and 0.8 μm. The coherent light beam 102 from the light source 100 passes through a collimating lens 104 which may be a GRIN lens or SEL-FOC lens. The light beam 102 then passes through a polarizing beam splitter (pbs) 106, and is then reflected by a pair of mirrors 108 and 110 to pass through a Faraday rotator 112, a half wave ({fraction (λ/)}2) plate 114, and another polarizing beam splitter (pbs) 116. The polarizing beam splitter 106 rejects vertically polarized light from the light beam 102 and allows horizontally polarized (or transverse electrical polarized) light to be transmitted to the mirrors 108, 110.

[0037] The Faraday rotator 112 rotates the polarization of the light beam 45° in one direction, and the half wave plate 114 rotates the polarization of the beam by 45° in the opposite direction to return it to horizontal polarization. The resultant polarization of the light beam after the combination of the Faraday rotator 112 and the half wave plate 114 is horizontal. The second polarizing beam splitter 116 further “filters” the light beam and transmits only horizontally polarized portions of the light beam to a solid or air gap etalon 118.

[0038] The etalon 118 may be a Virgo Optics Model ES254-010 having a reflectivity of 97.5% and a thickness of 2 mm. As known in the art, the parameters of the etalon 118 may be selected depending on the dimension of the laser cavity. The etalon 118 performs multiple tasks. First, the etalon 118 performs a strong selection for lasing of only one single longitudinal-mode of the laser cavity. Second, the etalon 118 reduces the laser's linewidth from approximately 100 kHz to approximately 15 kHz. Third, the etalon 118 reduces the detected noise by filtering out spontaneous emissions. Due to the etalon's reflectivity of 97.5%, the finesse of the etalon is 100 so that the detected spontaneous emission noise is reduced by a factor of 100. Finally, the etalon 118 reduces the detected spontaneous emission noise from an external optical amplifier 120 used for amplifying the power from the laser 58 and for implementing a coherent time domain reflectometry technique.

[0039] The light beam exiting the etalon 118 proceeds to a beam splitter 122 that divides the beam into two light beams progressing on two different paths 124 and 126. Path 124 is the light output path to the sensing fiber 52. The light beam traveling on the path 126 is reflected by a grating 128 to progress along path 130. The grating 128 further performs, along with the etalon 118, the function of selecting one single longitudinal mode of the laser for lasing. The reflected light traveling along path 130 passes through a lens 132 and returns to the back facet of the optical amplifier 100, becomes amplified by the amplifier 100, and leaves the front facet of the diode amplifier 100 down the path of light beam 102 again. As the optical amplifier 100 continues to provide gain, the horizontally polarized portion of the traveling light beam 102 becomes increasingly stronger, and the vertically polarized portion essentially disappears.

[0040] The light beam traveling on the path 124 is used for reflectometry measurements. The output light beam proceeds to a second Faraday rotator 134 and then to an optical plate or half wave plate 136 where a fraction of the light 138, hereinafter referred to as the reference light P_(ref) is reflected back toward the Faraday rotator 134 from the optical plate 136. The remaining light 140 is transmitted by the optical plate 136 through a lens 142 to an optical amplifier 120. The optical amplifier 120 can be, and preferably is, a fiber optical amplifier or semiconductor optical amplifier. The optical amplifier 120 is biased at an appropriate DC level, for example, 100 mA for a semiconductor optical amplifier. The amplified light is then launched into the sensing fiber 52 for reflectometry measurements. The half wave plate 136 is used if the gain in the amplifier 120 is substantially the same for all axes. The side of the half wave plate 136 facing the Faraday rotator 134 is coated with a reflective coating to generate the reflected reference light P_(ref) 138.

[0041] The polarization of the reference light, P_(ref) 138, reflected by the optical plate 136 is rotated 90° upon exiting the Faraday rotator 134. The reflected reference light is further deflected by the beam splitter 122 and the polarizing beam splitter 116 into a detector 144. The detector 82 may be a New Focus Model 1811. The detector 144 also functions as a signal generator that generates the analog signal F(t) 60 indicative of the received light.

[0042] The light traveling in the sensing fiber 52 is backscattered by a disturbance or fault. The backscattered light from the sensing fiber 52, herein referred to as the signal light, P_(sig), follows the same path back through the beam splitter 122 and polarizing beam splitter 116 as the reference light P_(ref) 138 and is also detected by the detector 144 and provided as a portion of the analog signal 60. The backscattered optical pulse signal P_(sig) is coherently mixed with the reference light P_(ref). The time-delay of the return pulse signal P_(sig) indicates the distance to the reflection point.

[0043] The analog signal 60, or F(t), is converted by the analog to digital converter 62 to the digital signal 64 wherein the digital signal 64 is expressed as a function F(nh), where h is the pulsing period of the analog signal 60 and n is the index of the sample being considered. The digital signal 64 is then stored for a time by the buffer 66 which then provides the digital signal, via signal 68, to the signal analyzer 70.

[0044] The signal analyzer 70 is used to conduct a time-domain wavelet analysis of the signal 60 and create the template signal 72, which is then compared to the stored signal 76 from the storage medium 80. Processing and analysis of the analog signal 60 to create the template signal 72 allows for specific features of the signal to be isolated and identified. Thus, comparison of the template signal 72 to a prestored signal is more likely to reveal the presence of an energy signature indicative of an event of interest, such as a rail break.

[0045] The technique for creating the template signal 72 will be described in general terms here. However, further description of this type of analysis, and devices useful for performing it, is found in U.S. Pat. No 5,262,958 entitled “Spline-Wavelet Signal Analyzers and Methods for Processing Signals” issued to Chui et al. That patent is incorporated herein by reference.

[0046] The signal analyzer 70 takes samples of the digital signal 68, the samples being F(0), F(2h), F(4h), F(6h) . . . , and multiplies them by a series of weights W⁻⁴, W⁻³, W⁻² . . . W₀, W₁, W₂, W₃, W₄, in a moving average operation to derive a plurality of zero-level scaling function coefficients c⁰(n). The scaling function coefficients c⁰(n) can be used to reconstruct the analog signal 60 as F⁰(t) where F⁰(t) represents that the signal so derived is an approximation to the original signal F(t).

[0047] A set of spline coefficients c⁰(n) is used as an input to an A_(n) memory (not shown) and a B_(n) memory (not shown). The A_(n) memory contains constants a_(n) which are used to derive c⁻¹(n) scaling function coefficients for the approximated signal F⁰(t). The B_(n) memory contains constants b_(n) which are used to derive d⁻¹(n) wavelet coefficients for the approximated signal F⁰(t). The coefficients c⁻¹(n) are used to derive a first-level approximated function F⁻¹(t). Similarly, the d⁻¹(n) set of coefficients is used to derive a first-level wavelet G⁻¹(t) as a compliment to the approximated signal.

[0048] In a similar manner, second-level wavelet coefficients d⁻²(n) are derived from the first-level scaling function coefficients c⁻¹(n) and second-level coefficients c⁻²(n) are also derived from the first-level spline coefficients c⁻¹(n). The derivation can be repeated for as many levels of resolution as is deemed necessary.

[0049] Referring now to FIGS. 4A-4 d, representative signals are depicted of the type that might be produced by the present invention. It should be understood that the signals depicted are exemplary only and are depicted for the purpose of explaining the functioning of the invention. As measured and processed, actual signals may appear quite different from those depicted here.

[0050]FIG. 4A shows an exemplary analog signal 60 as produced by the detector 144 of the laser 58. The signal 60 is shown as a function F⁰(t) that has a particular intensity or signal strength over time (t). The spikes 150, 152, 154, 156 in the signal 60 are indicative of laser pulsing. As shown, the intensity of the signal decays after each spike 150, 152, 154, 156. It can also be seen that the signal 60 is somewhat irregular due to the presence of noise or minor disturbances of the sensing fiber 52. It will be appreciated that the signal 60 depicts a laser that is pulsed approximately every 0.75 ms. The effect of one minor disturbance 157 can be seen affecting the decay of a laser pulse-induced spike. This disturbance might be caused by train or vehicular traffic or some other source.

[0051] A discontinuity 158 in the signal 60 is due to a rail break event. The event has occurred over a short period of time (approximately 0.25 ms) and creates a significant increase in the amplitude of the signal 60. As compared to the disturbance 157, the discontinuity 158 results from a greater release of energy occurring over a shorter period of time, thus accounting for its increased height and shorter duration.

[0052]FIG. 4B illustrates the digital signal F(nh) 64, obtained by processing the analog signal 60 via the analog-to-digital converter 62. It can be seen that the spikes 150, 152, 154 and 156 have been converted to discrete-time signals 160, 162, 164 and 166. The disturbance 157 and discontinuity 158 become discrete-time signals 167 and 168, respectively.

[0053]FIG. 4C depicts the template signal 72 that is achieved by wavelet analysis performed by the signal analyzer 70. The template signal 72 provides a series of recognizable wavelet coefficients 170, 172, 174, 176 which correspond to the discrete-time signals 160, 162, 164 and 166 of the digital signal 64. Wavelet signatures 178, 180 are also present for the discrete-time signals 167 and 168.

[0054]FIG. 4D depicts a stored signal 76 which represents the wavelet signature of a rail break event 182. As can be seen, the stored rail break signature 182 corresponds closely to the wavelet signature 180 for the rail break event as derived from the analog signal 60. As noted, the comparator 74 will compare signals 72 and 76 to determine whether there is a match for the stored signature 182 present in the template signal 72.

[0055] When a break 20 occurs, an energy signature 100 is released into the surrounding earth 32, as depicted in FIG. 1. When the rail break event occurs, it is typically characterized by a large energy release that will cause an intrusion or disturbance of the proximate sensing fiber 52 for one of the monitoring apparatuses 22, 24. As rail break events cause a large-magnitude energy release over a short period of time (e.g., 200,000 psi in less than 2 ms), the intrusion that these events cause to a sensing fiber is easily distinguishable from other events which might also cause an intrusion or disturbance of the fiber. Examples of such other events include passing trains or vehicles and animals, which should produce much smaller energy releases dispersed over a longer time period (e.g., 100 psi over 100 ms). The signals produced by these disturbances are subjected to wavelet analysis by signal analyzer 70 in order to detect and identify a spike or spikes having the characteristic signature of a rail break.

[0056] The characteristic signature of a rail break can be determined by simulation or by recording of an actual rail break under simulated conditions, and the signatures of other potential environmental intrusions can be measured as well. These signatures can then be subjected to signal analysis to identify distinguishing features of the signal produced during a rail break. Such a procedure is understood by one of skill in the art. Among other features, the short time duration and high magnitude of energy release may be used to detect and identify a rail break event. These features can be extracted via wavelet analysis, and those events which do not possess these features can be screened out by the signal analyzer 70. The signal analyzer 70 is programmed to detect signals having substantially the same components and characteristics as the recorded signal. Screening techniques are used to screen out signals that do not have these unique components and characteristics.

[0057] The monitoring assemblies 22, 24 are also capable of establishing the approximate location of the rail break event, as measured by the length of the sensing fiber.

[0058] In another aspect of the invention, the monitoring assemblies 22, 24 are useful for detecting other identifiable events, including the existence of flat spots on rail car wheels. Such flat spots on the wheel circumference are undesirable since they cause the train to become much more difficult to pull. Further, such deformations in the wheel may damage the track rails, ultimately leading to more rail breaks.

[0059] Operation of the system is essentially the same when used to detect flat spots on wheels as that described earlier with respect to the detection of rail break events. The energy signature associated with the passage of trains having such flat spots becomes the event of interest, and a signal representative of this type of energy signature will be stored in the storage medium 80. When a train having one or more wheels with flat circumference spots travels along the track section 12, the flat spots intermittently contact the track rails 14, 16 resulting in a periodic energy signal. The periodic energy signal is transmitted through the track and ground 32 to cause a disturbance of one of the sensing fibers, such as fiber 52. The periodic energy signal is detected in much the same manner as the rail break event energy signature 100 was detected.

[0060] While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. 

What is claimed is:
 1. A method of detecting a break event in a rail segment comprising: a) propagating energy from the break event to disturb a sensing fiber; b) generating a signal in response to the disturbance of the sensing fiber, the signal being indicative of the break event.
 2. The method of claim 1 further comprising the operation of detecting the break event disturbance by processing the signal.
 3. The method of claim 2 wherein the signal processing comprises wavelet analysis.
 4. The method of claim 3 wherein a template signal is created through the wavelet analysis.
 5. The method of claim 4 further comprising the operation of comparing the template signal to a stored signal representative of a rail break to determine whether a rail break event is present in the template signal.
 6. A method of detecting an event of interest associated with a rail segment comprising: a) disposing a monitoring apparatus having a particular length alongside and proximate a portion of the rail segment, the monitoring apparatus capable of determining the approximate location of an energy signature from an event of interest along the length of the monitoring apparatus; and b) receiving at the monitoring apparatus an energy signature corresponding to an event of interest and detecting the energy signature.
 7. The method of claim 6 further comprising the operation of generating an analog signal representative of the energy signature.
 8. The method of claim 7 further comprising the operation of examining the analog signal to determine whether an event of interest is present in the energy signature.
 9. The method of claim 8 wherein examination of the analog signal comprises the operations of deriving a template signal from the analog signal and comparing the template signal to a stored signal representative of the event of interest.
 10. The method of claim 6 wherein a plurality of monitoring apparatuses are disposed alongside adjoining portions of the rail section so as to provide a substantially continuous monitoring assembly.
 11. A monitoring apparatus for detecting a disturbance associated with a rail segment, the apparatus comprising an intrusion detection device disposed alongside a rail section, the intrusion detection device being operable to detect energy released from an event of interest associated with the rail segment.
 12. The monitoring apparatus of claim 11 wherein the intrusion detection device comprises a fiber optic sensing fiber.
 13. The monitoring apparatus of claim 12 wherein the intrusion detection device further comprises a laser for directing a beam of laser light through the sensing fiber.
 14. The monitoring apparatus of claim 12 wherein the intrusion detection device further comprises a signal generator for generating a signal indicative of a disturbance of the sensing fiber.
 15. The monitoring apparatus of claim 14 wherein the intrusion detection device further comprises a comparator for comparing the generated signal to a prestored signal representative of the event of interest.
 16. The monitoring apparatus of claim 15 further comprising a storage medium to contain a prestored signal representative of an event of interest.
 17. The monitoring apparatus of claim 15 further comprising a signal analyzer to process the generated signal to create a template signal for comparison to the prestored signal.
 18. The monitoring apparatus of claim 14 further comprising an analog to digital converter to convert the generated signal to a digital signal.
 19. The monitoring apparatus of claim 14 further comprising a buffer for periodic storage of the generated signal. 